Solar infrared absorbers



, following examples.

lihited States Patent Ofiice 3,298,898 Patented Jan. 17, 1967 3,298,898 SOLAR INFRARED ABSORBERS Walter George. Gall, Shellbourne, DeL, assignor to E. I.

This invention relates to the use of infrared light absorbers to reduce the heat transmission of constructions transparent to visible light.

Conventional vehicle Windshields, rear windows, side glass panels, and ceiling glass panels transmit all wavelengths of light about equally. The sun emits electromagnetic radiation over a wide, continuous band of wavelengths stretching from the ultraviolet to the far infrared region. Because of attenuation by adsorption by atrns pheric water vapor, carbon dioxide, and ozone, and scat tering by atmospheric dust particles, only a relatively narrow band of wavelengths, from 0.29 to 21 penetrates to sea level on the earth. The intensity of this radiation is peaked sharply at 0.50 so that radiation in the region from 0.29 to 040a, commonly called the near ultraviolet, comprises only 4% of the total solar energy reaching the earth, with the remaining 96% distributed almost equally between the visible (0.40 to 0.75 a) and the near infrared (0.75 to 2.1a). Therefore, it can be seen that by selectively absorbing or reflecting the infrared and transmitting the visible light in vehicle windows, one can decrease the heating effect of the sun on the interior of such vehicles.

It is an object of this invention to provide an absorber which absorbs infrared more than visible radiation.

This invention has as a further object the provision of an infrared absorber which can be incorporated in the polyvinyl butyral interlayer of safety-glass.

These objects are accomplished by the following invention in which an iron quinone oxime chelate is incorporated in the interlayer of safety-glass.

In the past, near infrared radiation has been absorbed by transition metal ions, many of which have weak absorption bands in the near infrared. Of these, the ferrous ion is highly selective, exhibiting little visible absorption. Two brands of such infrared absorbing glass depending on mixtures of metallic ions are available, namely Solex, made by Pittsburgh Plate Glass Company and EZ-I,

made by Libby-Owens-Ford. When made into standard Windshields using two 120 mil glass layers and a 15 mil polyvinyl butyral interlayer, the sandwich has a visible transmission of 69% and infrared transmission of 25%. The absorption bandwidth of these materials is 0.70 to 1.47 1. However, these metal oxides cannot be used in the interlayer which, being only the thickness of the glass, require absorbers that are much more intense.

The invention involves a group of iron quinone oxime chelates. They are iron chelates of o-quinone monoximes which are tautomeric with o-nitrosophenols.

. The details of preparing two such infrared absorbing iron chelates of o-quinone monoximes are disclosed in the Others can be prepared by substituting molecular equivalents of other aromatic hydroxy compounds for those used in the two examples.

Example 1 Sodium nitrite (7.15 g.) was dissolved in a solution of 0.1 mole of Z-naphthol and 4.0 g. of sodium hydroxide in 175 ml. of water at 0 C., and a cool solution of 7.3 ml. of concentrated sulfuric \acid in 15 m1. of water was then added dropwise, with vigorous stirring, keeping the temperature at 0 C. When the acid addition was completed, the mixture was stirred an additional two hours at 0 C. and the product was then separated by filtration,

washed and dried. To a solution of 5.20 g. of this product in 250 ml. of methyl alcohol, 3.92 g. of ferrous ammonium sulfate hexahydrate dissolved in 30 ml. of water was added to produce ferrous 1,2-naphthoquinone-l-oximate, which has the structure a (C01. Q0 J.

This chelate forms a greenish, black precipitate which is then separated by filtration, washed, and dried. In the above formula, n is 3 as the solution was herein prepared, however, It may be either 2 or 3. If the hexacoordinated product is prepared, the iron will have a net change of 1 so the isolated chelate is associated with some positive ion that is present during its preparation. Here it is associated with the ammonium ion from the ferrous ammonium sulfate. The chelate formed by this example is compatible with polyvinyl butyral, forming a green solution, and has sufficient thermal stability to permit mixing by extrusion. It has an absorption maximum at 780 my. and a peak visible transmission at 550 mu. Laminates prepared from 15 mil polyvinyl butyral and two 120 mil glass sheets have the characteristics shown in Table I.

TABLE I Concentration Percent Chelato of Ghelate Absorption Transmission in Interlaycr, Bandwidth, 111;: at Absorption Percent Maximum The ferric chelate shown in Table I is prepared the same as the ferrous chelate of Example 1, except 2.70 g. of ferric chloride hex-ahydrate are substituted for the ferrous ammonium sulfate of Example I.

Exam ple II A saturated aqueous solution of 14.3 g. of sodium nitrite was added dropwise, with vigorous stirring to a solution of 0.1 mole of 2,7-dihydroxynaphthalene in 200 ml. of 90% acetic acid which was kept at 0 C. After the addition was completed, the mixture was stirred for two hours at 0 C. The nitroso derivative was then isolated by adding 400 ml. of water, followed by filtration of the precipitated solid. Then 2.18 g. of the thus formed nitroso derivative were dissolved in 80 ml. of warm ethyl alcohol, to which 3.92 g. of ferrous ammonium sulfate dissolved in 20 ml. of water were added to form the ferrous chelate. The precipitate which formed was filtered, washed, and dried. The thus formed ferrous chelate, dissolved in a 15 mil thickness polyvinyl butyral sheet, had an infrared absorption band from 640-985 where the transmission was 7.5% at 0.1% concentration, and 2% at 0.2% concentration of the chelate.

TABLE II Wt. Percent Percent Trans- Dissolved in Absorption Absorption mission at 151) Mlil Thick Bandwidth, Peak, 1111.4 Abjslpraplgion O viny III C Bu tyral H Ferrous 1,2-naphthoquinone-2-oximate 0. 1 630-910 770 22 Ferrous 6-bromo-1,Z-naphthoquinone-loximate 0. 1 615-880 765 23 D 0.2 615-880 765 11 Ferrous 3-hydr0xy-1,2-naphthoquinone-loximate 0. 2 610-870 750 7. Ferrous 5-hydroxy-l,2-naphthoquiuone-1- oxiniate 0. 2 650-870 770 31 Ferrous 7-hydroxy-1,Z-naphthoquinone-l- (inmate 0. 2 650-970 800 s Ferrous chelate of 1,3-dintr0soresorciiiol (DNR) dispersion 0.2 650-970 825 29 Ferrous chelate from mixture of 0.5 mole (DNR) plus 1.0 mole of l-llitIOSO Z- naphthol 0. 1 600-900 760 4. 5 Ferrous chelate from mixture of 1.2 moles (DNR) plus 0.6 mole of l-uitroso-Z- naphthol I 0. 1 620-980 770 5 The chelates of this invention have the structure TABLE HI "I Percent Percent N O N:() Protection Visible Infrared 1| i 1 30 Increase Increase =O Fe OFc A A Unprotected (200 hrs.) 34 56 I T Dipped in 1% nickel dibutyldithiocarbamate. 8. 5 3. 5

n u 1% 2,2-dihydroxy-4-methoxy benzophenone with chelate 26. 5 3e Laminated Xtvith Solex gla ing pro ec ion l9 7. 5 Ar can be benzene, naphthalene or a rnulti-ring compound, n can be either 2 or 3 giving either ferric or forrous chelates. Also, if the dinitrosation product of a The dip ing in nickel dibutyl-clithiocarbamate is re- P P dihydroxy aromatic compound is converted to an iron ferred. chelate, two such quinone oxime chelate structures may 40 The infrared absorbing constructions of this invention be present on the single aromatic ring structure, as was are useful as welders goggles, sunglasses, and as devices produced in Example II. Other metals were tried in an interposed between the light source and the film in movie attempt to produce a series of chelated salts, but none of and slide projectors to protect the film from excess heat, these others were found satisfactory. in addition to their usefulness in vehicle windows.

Suitable amounts of the iron chelates of this invention I claim: in polyvinyl butyral are from 0.01 to 2%. The only 1. A polyvinyl butyral resin having dissolved the-rein reason found to stay within this range is the insufficient from 0.001 to 2 percent of an iron chelate having the infrared absorption below 0.01% and the sheet becomes structure too dark to see through under normal lighting if over 2% is used. At high concentrations, many of these che- NO N=O| lates are insoluble in polyvinyl butyral, causing a haze. H I I I l Where haze is not objectionable, an insoluble chelate =O* Fe oFe may be used by dispersing it in the polyvinyl butyral. Ar Ar The iron chelates of this invention are useful in any transparent medium in which they are soluble or dispersible. n n In general, such media are polar synthetic resins. Examples of such resins are polycarbonates, acrylics, and polyg g z g 2 i gfig zi g gg g g igg 22 235 amides. The infrared absorbers of this invention can be g gioup consisting of benzene and naphthalene which may incorporated in the resin by adding to the extrusion powbe substituted with a group selected from the group conder prior to extrusion or by melting in with the resins. Sistinn Ofh drox 1 and bmm 1 As an example of the utility of these absorbers in other 2 1 3} claim 1 gh'erein the aromatic rin Ar resins, 0.02% of the ferrous 1,Z-naphthoquinone-l-oxig is derived from naphthalene. mate was melt blended into Lucite 140, Du Pont acrylic ,3 The resin of Claim 1 wherein the iron chalate is resin. The mixture was then molded into a 75 mil sheet x ferrous 1,2-naphthoquinone-l-oxirnate. which had an absorptlon maximum at 780 (4% 4 The resin of claim 1 wherein the aromatic rin Ar mission) and an absorption bandwidth of 610910 III/.0. a

Table III shows the results of studies of weatherability 1s x zg g fi fj fii' having an hterla er formed using ferrous l,2-naphthoquinone-l-oximate in the pres- Y a S 1 y of polyvinyl butyral having dissolved therein from 0.01 ence of various ultraviolet stabilizers. This absorber was to 2 ercent of an iron chelate havin the structure tested as a 0.1% solution in polyvinyl butyral. The p g listed transmission changes are all in terms of the in- N "I crease in transmission overall at the visible maximum and infrared minimum after 600 hours of Fadeometer I exposure. This exposure Was carried out in accordance A O Fe E A OTe with the standard test method 16A-1957 of the American r r Association of Textile Chemists and Colorists. n n

where n is an integer selected from the group consisting 9. The safety-glass laminate of claim 7 wherein the of 2 and 3 and Ar is an aromatic ring derived from the iron chelate is ferrous 1,2-naphthoquinone-l-oximate. group consisting of benzene and naphthalene which may 10. The article of claim 9 wherein the ultraviolet stabe substituted with a group selected from the group conbilizer is nickel dibutyl-dithiocarbarnate. sisting of hydroxyl and bromyl. 5 11. The safety-glass laminate of claim 5 wherein the 6s The article of claim 5 wherein the aromatic ring aromatic ring Ar is derived from benzene. Ar is derived from naphthalene.

7. The article of claim 6 wherein said interlayer is No references cited.

protected with an ultraviolet stabilizer.

8. The article of claim 7 wherein said interlayer is 10 MORRIS SUSSMANPrmary Exammer' provided with an ultravioletstabilizer in a separate layer. W. J. VAN BALEN, Assistant Examiner. 

5. A SAFETY-GLASS LAMINATE HAVING AN INTERLAYER FORMED OF POLYVINYL BUTYRAL HAVING DISSOLVED THEREIN FROM 0.01 TO 2 PERCENT OF AN IRON CHELATE HAVING THE STRUCTURE 